U.S. Pat. No. 4,274,822 refers to an apparatus for forming seal liners of thermoplastic material within closure cap shells. The apparatus is purported to include a plurality of movable dies each having an inner die and an annular outer die, both of which are movable up and down in relatively slidable relation with each other and arranged so that the inner die takes it lowermost position after the outer die has taken its lowermost position. A downward movement of the outer die is restricted so that a constant clearance may be maintained between its lower end and an internal surface of a cap shell to be worked with, and so that an annular foaming chamber of a constant capacity is formed beneath the lower end of the outer die. A plurality of gas discharging grooves are provided so as to be communicated with the foaming chamber.
U.S. Pat. No. 5,332,381 refers to an apparatus for forming liners of thermoplastic material within closure shells. The apparatus is purported to include a movable die having an inner punch member and an annular outer mold member, both of which are moveable up and down in relatively slidable relation with each other and arranged so that the inner punch takes its lowermost position after the outer mold member has taken its lowermost position. As the inner punch moves into its lowermost position, thermoplastic material is forced through radial grooves so that a thick annular pad portion of seal liner may form beneath the lower end wall of the outer mold member.
U.S. Pat. No. 5,800,764 refers to an external venting method for forming a closure liners, in which venting means are provided by a plurality of venting passages formed in an outer surface of a liner sleeve of a liner-forming assembly when properly positioned within the closure. A liner tip coaxially disposed in the sleeve is advanced to compress a moldable plastic liner-forming material between the closure, the liner tip, and the sleeve, so that gas may vent therefrom to a region external to the sleeve.